This study examined the behavior of granular activated carbon (GAC) in a hybrid GAC-microfiltration process, which was used to simulate an anaerobic fluidized membrane bioreactor. GAC can exhibit two major beneficial roles in reducing membrane fouling, namely, (1) GAC scours the membranes to limit the cake layer formation and facilitate cake layer removal; (2) GAC tends to absorb potential foulants to reduce the interaction of foulants with the membranes. However, several detrimental effects of GAC on membrane performance were also observed. For example, (1) GAC appeared to release micro- and nanoscaled fine carbon particles, which can form potential foulants. (2) GAC abrasion can induce partial membrane integrity loss, which was proven by membrane permeability increase and microscopic autopsy. Interestingly, it was found that the GAC size had little influence on the scouring-enhanced filtration performance and scouring-induced membrane damage. The properties of the membrane materials were more important in determining the extent of integrity loss of the membrane after GAC abrasion. A membrane with good elongation properties (e.g. polyvinylidene fluoride) and GAC having a suitable size (i.e. less energy consumption) with good stability (i.e. releasing less fine carbon particles) is recommended for the hybrid fluidized GAC-membrane filtration process.
The authors thank Jillinda Toh, Steven Limbra, Cui Xian Liou, Yuanyuan Wang, and Alvin Chew for their kind help. This research grant is supported by the Singapore National Research Foundation under its Environmental & Water Technologies Strategic Research Programme and administered by the Environment & Water Industry Programme Office (EWI) of the PUB. The EDB is also acknowledged for funding the Singapore Membrane Technology Centre (SMTC), Nanyang Technological University.
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